Chairman Lord Deben’s letter to the Business, Energy and Industry Strategy (BEIS) Secretary voices doubts as to whether the Department for Transport’s (DfT) business case for the third runway is in line with meeting the Fifth Carbon Budget and 2050 emissions targets.

The committee previously set out a planning assumption for aviation emissions in 2050 to be at the same level as they were in 2005.

This is possible due to technological innovations and operational improvements and it’s thought the industry can grow by 60% over the period without breaking the limit.

However, the Heathrow expansion business case presented by the government works on the basis of aviation emissions being 15% higher than in the CCC plan. Lord Deben suggests this could have implications on whether the controversial investment is even worth making.

He also says if this is due to a discovery that current emissions are higher than initially anticipated, all sectors would have to prepare for correspondingly higher emission reductions in 2050, something that he thinks is very unlikely to be possible.

Transport Secretary Chris Grayling is due to present evidence to MPs next week about how the proposed project would comply with air quality plans.